Timer device for an electrostatic gas purifying system



July 14, 1964 R. P. FLAGG 3,140,935

TIMER DEVICE FOR AN ELECTROSTATIC GAS PURIFYING SYSTEM Filed Sept. 29. 1960 2 Sheets-Sheet l IONIZER i 24 7 cowl AuTo.

INVENTOR. RAYMOND P. FLAGG ATTORNEY United States Patent TIMER DEVICE FOR AN ELECTRQSTATIC GAS PURIFYING SYSTEM Raymond P. Flagg, Golden Valley, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Filed Sept. 29, 1960, Ser. No. 59,410 4 Claims. (Cl. 55-139) This invention relates generally to sequencing apparatus, and more specifically to a timer mechanism for controlling the operation of an electrostatic gas purifying system.

In systems of the type described designed for residential use Where the ionizing and collecting electrodes are located in the cold air return of the buildings forced air heating system, means must be provided for periodically shutting down the filter system so that the dust accumulation on the collecting electrodes may be washed olf. Since the ionizing and collecting electrodes of electrostatic gas purifying systems are normally maintained at a relatively high potential, it is necessary for safety reasons to insure that the home owner cannot come into contact with this high voltage. Also, for proper operation of the filter unit it is necessary that the ionizing and collecting electrodes be relatively dry before the high voltage is again applied to them after they have been removed and washed. Should the power he turned on while the electrodes are still wet, serious arcing is likely to occur between the closely spaced electrodes which is objectionable from both a noise standpoint and because serious damage may result to the system itself.

My invention is concerned with a novel device designed for use with an electrostatic air cleaner of the residential type, which is effective to completely deenergize the system when the access door is opened for removal of the ionizing and collecting electrodes so that they may be Washed and which insures that these electrodes are completely dry before the power is again applied to the systern. My timing device is arranged to cooperate with the handle on the access door of the duct mounted electrostatic air cleaner such that when the door is unlocked, a switch operating mechanism is brought into play to break the circuit to the primary circuit of the high voltage power supply and to make a circuit to a timing motor which is effective to reclose the circuit to the power supply after a predetermined delay of suflicient length to allow the ionizing and collecting electrodes to dry completely. Also, at the same time that the handle to the access door is turned to unlock the door, a mechanism is operated to short out any voltages which may exist in the system to thereby render the equipment harmless to the home owner.

It is accordingly an object of the present invention to provide an improved control device for use with an electrostatic air cleaner.

Another object of my invention is to provide an improved control device which operates to insure that the ionizing and collecting electrodes are completely dry subsequent to washing before the system is again energized.

Still another object of the present invention is to provide in a single device a means for controlling the sequence of operation of an electrostatic air cleaner and a means for rendering the system completely safe when maintenance is required.

Cir

Patented July 14, 1964 Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode of applying that principle.

In the drawings,

FIGURE 1 is a perspective view of the cabinet which houses the electrostatic air cleaner equipment.

FIGURE 2 is a schematic diagram of the electrical circuit for an electrostatic air cleaner.

FIGURE 3 is a view, with portions broken away, of the apparatus incorporating the invention, and

FIGURE 4 is a bottom view of FIGURE 3.

Referring now to FIGURE 1 in which is shown the manner in which the electrostatic air cleaner incorporating the features of the invention is mounted in the cold air return duct 10 of the buildings forced air heating system, inserted crosswise to the flow of air through the duct 10 is a housing 12 which is designed to contain the ionizing and collecting electrode assembly (not shown). Removably hinged to the housing 12 at 14 is an access door 16 which may be unlatched and opened by turning the handle is thereon approximately from the position shown. The access door 16 is made up of a U-shaped cover member 29 and a bottom plate 22 which together define a space in which various electrical circuits, later to be described, are contained. In FIGURE 1 the access door 16 is shown as being able to open from the top down, but where the particular installation requires it, the access door 15 may be mounted so as to open from the bottom up and can even be removed completely from the housing 12 by removing the hinge pin from the hinge 14.

Mounted in the upstream end of the housing 12 is a conventional ionizer. As shown schematically in FIG- URE 2, the ionizer has a plurality of spaced parallel plates 24 which are connected to the grounded housing 12. In between each of these parallel plates is strung an ionizing wire 26. The wires are mounted at their extremities to the casing 12 by electrical insulators and are connected to a positive source of power so that as gas or air passes through the ionizer, the foreign particles contained therein are charged.

Downstream from the ionizer and also mounted in housing 12 is a collecting unit or collector which is made up of a plurality of oppositely charged parallel plates.

One set of plates 28 which consists of every other plate is connected to the positive source of power. The other set of plates 30 spaced between the positive plates are connected to the housing 12 and thus also grounded. As the charged foreign particles in the gas pass into the collecting unit, they are attracted to the plates of the opposite charge and are collected on these plates.

The high voltage which is required for proper operation of the gas cleaning equipment is developed by means of a step-up transformer 32, the primary winding of which is normally connected to a source of volt 60 cycle current and the secondary winding 36 of which supplies energy to a voltage doubler rectifier circuit indicated generally by the numeral 38. The output voltage appearing at junction 40 of the power pack is approximately two times the maximum voltage developed across the secondary winding 36, but is direct current rather than alternating current. A conductor 42 is used to apply this voltage to the positive ionizing wire assembly 26. The high voltage collector plates 28 are also connected to the junction 40 by means of the conductor 42 and a current limit ing resistor 44. V

The primary Winding 34 of the step-up transformer 32 receives its input through a control circuit, and since the invention is centered around this control circuit, it will be explained in greater detail. The input terminals to the apparatus are identified by the numerals 4-6 and 48 and are adapted to be connected to a source of alternating current at normal line voltage. Junction 48 is grounded at point 50. Located in the control circuit of the electro-static gas purifying equipment is a plurality of switches including a double pole single throw power Orr-Off switch 52, a single pole single throw cam operated switch 54, and a single pole double throw cam oper-- ated switch 56. For safety reasons, there is provided a plurality of interlock switch contacts 58 through 66 which are normally closed when the access door 16 is closed, but which open to break the circuits when the access door is opened. A conductor 68 connects the input terminal 46 through the interlock contacts 62 to a first pole 70 of the double pole single throw switch 52. A conductor 72 connects the contact '74 associated with pole 78 to a junction 76. Junction 76 is the common point between the contact 78 which is associated with the single pole switch 54 and the pole 80 of the cam operated single pole double throw switch 56. A conductor 82 connects the contact 84 associated with switch 56 through the interlock contacts 60 to the conductor 86 which in turn is connected to one side of an indicating device 88. The other side of indicator 88 is connected by way of conductor 90, interlock contacts 58, and a conductor 92, to the primary winding terminal 94 of the step-up transformer 32. Finally, a conductor 96 connects the other primary winding terminal 98 through the interlock contacts 66 to the grounded input terminal 48. When the air cleaning system is in its normal operating condition, switch 52 is closed so that a current path may be traced from input terminal 46 through conductor 68, interlock contact 62, the pole '70 of switch 52, conductor 72, switch 56, conductors 82 and 86, indicator 88, conductors 90 and 92, the primary winding 34- of transformer 32, and conductor 96 to the other input terminal 48. The current normally flowing through this path energizes the transformer 32 and causes a relatively high potential to be induced across the secondary winding 36. As mentioned previously, this potential is multiplied and rectified by the voltage doubler circuit 38 and applied to the ionizing and collecting sections of the equipment. When the switch 52 is thrown to its off position the current flow to the primarywinding 34 is interrupted and hence no voltage is applied to the ionizing and collector sections.

A timing motor 100 is adapted to be connected across the source of line voltage whenever the single pole double throw cam operated switch 56 is moved from its position in contact with contact 84- to a position in contact with contact 102. Except for a blower or fan 184, the portion of the circuit to the left of the dash line 186, which is drawn through the interlock contacts 58 through 66, may conveniently be located in the living area of the building where the air cleaning equipment is utilized. The fan or blower 104 is contained in the furnace of the hot air heating system and is therefore generally located in the basement area. The blower 104 may be energized in three different ways. First of all the blower may be operated continuously by throwing the single pole double throw switch 108 from the position marked automatic to the position marked continuous or in the alternative, may be operated automatically under control of the thermostat device 110. It can be seen that the thermostat 110 and the switch 108 can be used to connect the blower 104 directly across the source of input voltage. The third way in which the blower 1'94 can receive its operating current is through the following path: From input terminal 4-6, through conductor 68,

through switch 52 and conductor 72, through switch 54 and the other pole 111 of switch 52, through interlock contacts 64-, a conductor 112, the fan motor 104 and the conductor 96 back to the grounded input terminal 48.

When the system is operating in its normal manner, the On-Oif switch 52 is in its on position and the cam operated switch 56 is in a position such that current flows through the primary winding 34- of the step-up transformer 32. This path has been described previously. Since the capacitors in the voltage doubling circuit 38 and the ionizer and collector sections of the equipment are capable of storing electricity for a relatively long period of time, means must be provided for rendering the system safe from electrical shock hazard should the home owner wish to remove the ionizing and collecting sections for washing. In other words, means are required for completely removing the stored electricity when the access door to the system is opened. Should the home owner forget or fail to turn the power oil by means of the On-Off switch 52, the apparatus of this invention, which will be described more fully hereinbelow, comes into play to render the system harmless. First of all, upon turning the handle 18 on the access door 16 the cam operated switches 54 and 56 are moved from the position in which they are shown in FIGURE 2 to their alternate positions. Moving of switch 56 from its p0sition in contact with contact 84 to its position in contact with contact 102 breaks the circuit to the primary winding 34 of the transformer 32 and connects in the timing motor 11M directly across the input supply. The turning of the handle 18 also causes a grounded shorting bar 114 to bridge the contacts 116 and 118 which are connected directly across the current limiting resistor 44 to thereby short out any voltage that may exist in the ionizer, the collector, or the capacitors in the voltage doubling circuit 38.

The purpose of the timing motor is to insure that the ionizer and collector are completely dry subsequent to washing before the power is again applied to the primary winding of the step-up transformer 32. If the power were applied while these electrodes were still wet or damp, serious arcing would occur in the ionizer and collector which may cause failure of one or more of the components in the system and even if not, the noise created thereby would be objectionable to the home owner. When the home owner has finished washing the electrodes, replaced them in the housing 12, closed and latched the access door 16, and placed the switch 52 in the on position, the primary winding 34 of the transformer 32 remains in a deenergized condition because the cam operated switches 54 and 56 remain in the position in which they were placed when the handle was originally turned to open the access door. That is, switch 54 is closed against its associated contact 78 and switch 56 is closed against its associated contact 102. With switch 54 closed, a current path may be traced from the input terminal 46 through conductor 68, through the interlock contacts 62, through the pole 70 of the On-Gft' switch 52, through conductor 72, through switch 54, through pole 111 of switch 52, through conductor 112, through the blower motor 164 and back to the grounded input terminal 48. The blower motor 104 is therefore energized and causes a current of air to pass over the ionizing and collecting electrodes located in the duct work 10 to promote their drying. At the same time, an electrical current flows through switch 56 and contact 102, through the timing motor 100 and conductor 96 back to the grounded input terminal 48. The timing motor is therefore energized and causes a cam, indicated schematically by the dashed lines 120, to rotate at a predetermined rate. After this predetermined time has elapsed, the cam is effective to open the switch 54 to thereby put the blower motor 104 under control of the thermostat and to move the switch 56 into contact with contact 84 to again provided a current path to the primary winding 34 of the transformer 32. The time that it takes for the cam to rotate so as to place the switches in this last mentioned condition is made sufliciently long to insure that the ionizing and collecting electrodes are completely dry.

FIGURES 3 and 4 illustrate the switch operating and timing mechanism of this invention. FIGURE 3 is a side elevation of the apparatus with a portion of the bottom plate 22 broken away to reveal the mechanism. FIG- URE 4 is a bottom view of FIGURE 3. As shown in FIGURE 4, a U-shaped mounting bracket 124 is secured to the bottom plate 22 by means of the fastening members 126. Passing through a hole 128 in the bottom plate 22 and through another hole provided in the mounting bracket 124 is a shaft 130 having a rectangular cross section. A latch member 132 is aihxed to shaft 1311 and held in a position abutting the bottom plate 22 by means of a spring 134. Projecting from the housing 12 but not shown in FIGURE 1 is a hasp which is designed to pass through the slot 136 cut in the bottom plate 22. The latch member 132 passes through the hasp and normally holds the access door assembly 16 locked against the housing 12.

Also connected to the shaft 131) is a linkage 138 which is keyed to said shaft such that when the shaft is rotated, linkage 138 also rotates. A gear rack 14% is riveted to the linkage 138 at point 142 but is free to rotate about the rivet. Afiixed to the underside of the mounting bracket 124 is the timing motor ltit). The shaft of motor 1% passes through a hole cut in the mounting bracket and has affixed thereto the cam 120 and a guide disk 122. Sandwiched between the cam 120 and guide disk 122 is a circular member 146 having gear teeth cut on a predetermined portion of its circumference. The rack member 140 is held in a position to cooperate with the gear member 146 by means of a tension spring 148.

FIGURE 4 illustrates quite clearly the manner in which the two switches 54 and 56 are mounted so as to be operated by the cam member 120. The switches 54 and 56 are sandwiched between a plate 150 and the mounting bracket 124 and held in place by fastening members 152 which pass through the entire assembly and are screwed into holes tapped in the mounting bracket 124. A hole 154 is drilled through the plate 150 which accommodates the ear 156 of a switch operating lever 15%. Likewise, a hole is drilled in the mounting bracket 124 directly opposite the hole in the plate 150 and accommodates the car 160 of the switch operating lever 158. The lever 153 is therefore free to rotate about an axis passing through these two holes.

A rivet 162 is used to secure a rod 164 to the linkage 138. The rivet 162 is sized, however, to permit the rotation of the rod 164 when the linkage 138 is moved. A slot 166 is cut lengthwise in the rod 164 and a rivet 168 is passed therethrough and affixed to the mounting bracket 124 so that the rod 164 is free to slide back and forth when the linkage 138 is rotated. The end of the rod 164 is notched to accommodate the shorting bar 114 (not shown in FIGURE 3) which is used to bridge the contacts 116 and 118 to short out the electrical charge which may be present in the system.

When the handle 18 is rotated approximately 90 in the clockwise direction (as viewed in FIGURE 3), the shaft 130 to which the handle is attached is also rotated. The latch 132, being connected to shaft 130 therefore rotates thereby allowing the hasp on the housing 12 to be removed from the slot 136 in the bottom plate 22 when the access door is pulled outward. The turning of the handle 18 also rotates the linkage 133 and causes the rack 140 to engage the teeth on the gear member 146 and rotate the cam 120. Since the gear 146 has teeth only on a predetermined portion of its periphery, the cam 120 is rotated by the rack 140 only by a distance sufiicient to allow the switch operating lever 158 to drop off the projection 121 on cam 120. When lever 158 falls off the projection 121 the switches 54 and 56 close against their respective contacts 7 3 and 102 to break the circuit to the primary of the power supply transformer 32 and connect in the timing motor. After the ionizing and collecting electrodes have been washed and replaced in the housing 12, the access door reclosed, and the On-Otf switch moved to the on position, current is supplied to both the timing motor ltitl and the blower motor 104. The blower continues to operate thereby drawing air through the duct 10 and the electrodes contained in the housing 12 to facilitate their drying. Since the cam is attached to the shaft 144 of the timing motor 100, this cam turns at a predetermined rate, for example, one revolution every three hours, and at the end of this predetermined delay the projection 1211 again moves against the switch operating plate 158. When the switch plate 153 has depressed the buttons on the switches 54 and 56, the switch 54 is again opened to break the circuit to the blower motor 104 and the switch 56 is moved from its position in contact with contact 102 to its position in contact with contact 84. The cycie is therefore completed and power is again applied to the primary winding 34 of the step-up transformer 32.

The portion of the periphery of the gear 146 occupied by gear teeth is determined by the minimum time that it takes for the electrodes to dry. 'If the home owner should open the access door, remove the ionizer and collector sections and reclose the door without having switched the manual On-Olf switch to the off position, the timer motor would begin to rotate as soon as the door is closed. If he should be delayed after Washing the electrodes and does not immediately replace them in the housing 12, the cam and gear will continue to rotate in the direction of the arrow. If when he subsequently opens the door to reinsert the still wet electrodes, there is still sufficient time to allow the electrodes to dry thoroughly, the rack 14-41 will slide along the toothless portion of the gear 146 and will not engage the gear. However, if to long a delay has intervened between the time that the access door was reclosed and the time at which the home owner desires to reinsert the wet elec trodes, the gear 146 will have traveled sufficiently far so that the rack 141 will engage the tooth portion of the gear 146 and the cam 121) will be carried around to its starting position when the door is again opened to insert in the electrodes. This insures that the electrodes will be allowed to dry for the entire delay period.

The switch plate 153 is provided with a pair of fingers one of which is raised a small amount beyond the other. The reason for this is that in the type of snap switches 54 and 56 employed, a differential always exists. Since it is desired that the fan motor be disconnected from the circuit before the contact to the timing motor is broken, the raised finger is associated with the switch 54.

Having now described my invention, it will be understood that various changes and modifications may be resorted to without departing from the spirit of, or sacrificing any of the advantages of the invention, and I deem myself entitled to all such variations and modifications as fail within the scope of the claims appended hereto.

What I claim as new and desire to protect by Letters Patent is:

1. In an electrostatic air cleaner of the type having a plurality of electrodes adapted to be mounted in the ducts of a forced air system and removable therefrom through an access opening in the ducts for washing, means for insuring that the electrodes are dry before the air cleaner is reenergized after washing comprising: power supply means for energizing the electrostatic air cleaner; motor means, said motor means having an output shaft; terminal means adapted to be connected to a source of alternating current; switch means having a first position wherein said terminal means are electrically connected to said power supply means and a second position wherein said terminal means are electrically connected to said motor means; a door adapted to be hinged on the duct and to close the access opening; latch means for locking said door in a closed position; a handle associated with said latch means and rotatable to lock or unlock said door; toothed rack means operably connected to said handle and adapted to be moved axially upon rotation of said handle; cam means driven by said motor means and in operative engagement with said switch means; rotation of said output shaft of said motor means through a predetermined angular distance less than a complete rotation defining a time delay period; and a gear having a toothed portion and a blank portion on its periphery, said gear being fixed on said output shaft, said blank portion of the periphery of said gear being in operative engagement with said rack means during the initial portion of said time delay period and said blank portion thereof being in engagement with said rack means when said gear is in all other angular positions, said rack means coacting with said gear upon rotation of said handle so that said cam is in a position corresponding to the initial portion of said time delay period whenever said door is opened, said cam thus being effective to place said switch means in said second position so that said motor means is energized, said cam means then being driven by said motor means to return said switch means to said first position after said time delay period, said period being sufficiently long to allow said electrodes to dry after washing.

2. In an electrostatic air cleaner of the type having a plurality of electrodes adapted to be mounted in the ducts of a forced air system and removable therefrom through an access opening in the ducts for washing, means for insuring that the electrodes are dry before the air cleaner is reenergized after washing comprising: power supply means for energizing the electrostatic air cleaner;

motor means; first terminal means adapted to be connected to a source of alternating current; second terminal means adapted to be connected to the blower of the forced air system; switch means having a first position wherein said first terminal means are electrically connected to said power supply means and a second position wherein said first terminal means are electrically connected to said second terminal means and to said motor means; a door adapted to be hinged on the duct and to close the access opening; latch means for locking said door in a closed position; a handle associated with said latch means and rotatable to lock or unlock said door; toothed rack means connected to said handle and adapted to be moved axially upon rotation of said handle; a rotary cam driven by said motor means and adapted to operate said switch means; rotation of said cam through a predetermined angular distance less than a complete rotation defining a time delay period; and a gear having a toothed portion and a blank portion on its periphery, said gear being fixed to said cam, said blank portion of the periphery of said gear being in operative engagement with said rack means during the initial portion of said time delay period and said blank portion thereof being in engagement with said rack means when said cam and said gear are in all other angular positions, said rack means co-acting with said gear upon rotation of said handle so that said cam is in an angular position corresponding to the initial portion of said time delay period whenever said door is opened, said cam thus being effective to place said switch means in said second position so that said second terminal means and motor means is energized, said cam means then being driven by said motor means to return said switch means to said first position after said time delay period, said period being sufficiently long to allow said electrodes to dry after washing.

3. In an electrostatic gas purifying system of the type having a plurality of electrodes mounted in a cabinet which is adapted to be mounted in the ducts of a forced air system of a building so that the air passes over the electrodes, the electrodes being removable from the cabinet through an access opening therein for washing, means for insuring that the electrodes are dry before they are reenergized after washing comprising: a door hinged on the cabinet and adapted to close the access opening therein; power supply means for supplying a relatively high electrical potential to said electrodes, latch means on said door for locking said door in a closed position; a handle associated with said latch means and rotatable to lock or unlock said door; toothed rack means connected to said handle and adapted to be moved axially upon operation of said handle; a timer motor, said timer motor having an output shaft; a rotary cam mounted on said shaft and rotatable thereby, rotation of said cam through a predetermined angular distance less than a complete rotation defining a time delay period; a gear having a toothed portion and a blank portion on its periphery, said gear being fixed to said cam, said blank portion of the periphery of said gear being in operative engagement with said rack means during the initial portion of said time delay period and said blank portion thereof being in engagement with said rack means when said cam and said gear are in all other angular positions; first terminal means adapted to be connected to a source of alternating current; second terminal means adapted to be connected to the blower of the forced air system; and switch means operable by said cam and having a first position wherein said first terminal means are connected to said power supply means and a second position wherein said first terminal means are con nected to said second terminal means and to said timer motor, said rack means co-acting with said gear upon rotation of said handle so that said cam is in a position corresponding to the initial portion of said time delay period whenever said door is opened, said cam thus being effective to place said switch means in said second position so that when said door is closed said second terminal means and said timer motor are energized, said cam then being driven by said timer motor to return said switch means to said first position after said time delay period, said period being sufficiently long to allow said electrodes to dry after washing.

4. In an electrostatic gas purifying system of the type having a plurality of electrodes mounted in a cabinet which is adapted to be mounted in the ducts of a forced air system of a building so that the air passes over the electrodes, the electrodes being removable from the cabinet through an access opening therein for washing, means for insuring that the electrodes are dry before they are reenergized after washing comprising: a door hinged on the cabinet and adapted to close the access opening therein; power supply means for supplying a relatively high electrical potential to said electrodes, said power supply means being mounted on said door; normally closed door interlock switch means which open when said door is opened; latch means on said door for locking said door in a closed position; a handle associated with said latch means and rotatable to lock or unlock said door; toothed rack means connected to said handle and adapted to be moved axially upon rotation of said handle; a timing motor mounted on said door, said timing motor having an output shaft; a rotary cam mounted on said shaft and rotatable thereby, rotation of said cam through a predetermined angular distance less than a complete rotation defining a time delay period; a gear having a toothed portion and a blank portion on its periphery, said gear being fixed to said cam, said blank portion of the periphery of said gear being in operative engagement with said rack means during the initial portion of said time delay period and said blank portion thereof being in engagement with said rack means when said cam and said gear are in all other angular positions; first terminal means adapted to be connected to a source of alternating current; second terminal means adapted to be connected to the blower for the forced air system; and switch means operable by said cam and having a first position wherein said first terminal means are connected to said power supply means through said interlock switch means and a second position wherein said first terminal means are connected to said second terminal means and to said timer motor through said interlock switch means, said rack means co-acting with said gear upon rotation of said handle so that said cam is in a position corresponding to the initial portion of said time delay period whenever said door is opened, said cam thus being effective to place said switch means in said second position so that when said door is closed said second terminal means and said timer motor are energized, said cam then being driven by said timer motor to return said switch means to said first position after said time delay period, said period being sufiiciently long to allow said electrodes to dry after washing.

References Cited in the file of this patent UNITED STATES PATENTS 2,088,499 Warner July 27, 1937 2,129,783 Penny Sept. 13, 1938 2,494,822 MacKenzie Jan. 17, 1950 2,604,184 Warburton et a1 July 22, 1952 10 3,054,245 Aron Sept. 18, 1962 

1. IN AN ELECTROSTATIC AIR CLEANER OF THE TYPE HAVING A PLURALITY OF ELECTRODES ADAPTED TO BE MOUNTED IN THE DUCTS OF A FORCED AIR SYSTEM AND REMOVABLE THEREFROM THROUGH AN ACCESS OPENING IN THE DUCTS FOR WASHING, MEANS FOR INSURING THAT THE ELECTRODES ARE DRY BEFORE THE AIR CLEANER IS REENERGIZED AFTER WASHING COMPRISING: POWER SUPPLY MEANS FOR ENERGIZING THE ELECTROSTATIC AIR CLEANER; MOTOR MEANS, SAID MOTOR MEANS HAVING AN OUTPUT SHAFT; TERMINAL MEANS ADAPTED TO BE CONNECTED TO A SOURCE OF ALTERNATING CURRENT; SWITCH MEANS HAVING A FIRST POSITION WHEREIN SAID TERMINAL MEANS ARE ELECTRICALLY CONNECTED TO SAID POWER SUPPLY MEANS AND A SECOND POSITION WHEREIN SAID TERMINAL MEANS ARE ELECTRICALLY CONNECTED TO SAID MOTOR MEANS; A DOOR ADAPTED TO BE HINGED ON THE DUCT AND TO CLOSE THE ACCESS OPENING; LATCH MEANS FOR LOCKING SAID DOOR IN A CLOSED POSITION, A HANDLE ASSOCIATED WITH SAID LATCH MEANS AND ROTATABLE TO LOCK OR UNLOCK SAID DOOR; TOOTHED RACK MEANS OPERABLY CONNECTED TO SAID HANDLE AND ADAPTED TO BE MOVED AXIALLY UPON ROTATION OF SAID HANDLE; CAM MEANS DRIVEN BY SAID MOTOR MEANS AND IN OPERATIVE ENGAGEMENT WITH SAID SWITCH MEANS; ROTATION OF SAID OUTPUT SHAFT OF SAID MOTOR MEANS THROUGH A PREDETERMINED ANGULAR DISTANCE LESS THAN A COMPLETE ROTATION DEFINING A TIME DELAY PERIOD; AND A GEAR HAVING A TOOTHED PORTION AND A BLANK PORTION ON ITS PERIPHERY, SAID GEAR BEING FIXED ON SAID OUTPUT SHAFT, SAID BLANK PORTION OF THE PERIPHERY OF SAID GEAR BEING IN OPERATIVE ENGAGEMENT WITH SAID RACK MEANS DURING THE INITIAL PORTION OF SAID TIME DELAY PERIOD AND SAID BLANK PORTION THEREOF BEING IN ENGAGEMENT WITH SAID RACK MEANS WHEN SAID GEAR IS IN ALL OTHER ANGULAR POSITIONS, SAID RACK MEANS COACTING WITH SAID GEAR UPON ROTATION OF SAID HANDLE SO THAT SAID CAM IS IN A POSITION CORRESPONDING TO THE INITIAL PORTION OF SAID TIME DELAY PERIOD WHENEVER SAID DOOR IS OPENED, SAID CAM THUS BEING EFFECTIVE TO PLACE SAID SWITCH MEANS IN SAID SECOND POSITION SO THAT SAID MOTOR MEANS IS ENERGIZED, SAID CAM MEANS THEN BEING DRIVEN BY SAID MOTOR MEANS TO RETURN SAID SWITCH MEANS TO SAID FIRST POSITION AFTER SAID TIME DELAY PERIOD, SAID PERIOD BEING SUFFICIENTLY LONG TO ALLOW SAID ELECTRODES TO DRY AFTER WASHING. 